1. Field of the Invention
The present invention relates to a hydrophilic polycarbodiimide polymer, a pulp-like material consisting of said hydrophilic polycarbodiimide polymer, and a process for producing said polymer or said material.
2. Prior Art
Polycarbodiimides, particularly aromatic polycarbodiimides are known to have high heat resistance and are used as a thermosetting molding material or the like by, for example, subjecting them in a powder form to hot pressing.
Processes for producing a polycarbodiimide are disclosed in, for example, Japanese Patent Application Kokai (Laid-Open) No. 61599/1976; D. J. Lyman et al., "Die Makromol. Chem., 67, 1 (1963)"; and E. Dyer et al., "J. Am. Chem. Soc., 80, 5495 (1958)". In these processes, as the polymerization solvent, there are used hydrocarbons (e.g. benzene), o-dichlorobenzene, etc.; the monomer concentration is 10-25% by weight; and there are used, as the organic diisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate and various other diisocyanates. The polycarbodiimides produced according to these processes have a powder form. In the above documents, mention is also made of a film produced by taking out the polymer from the reaction system after 10 minutes from the start of reaction and casting the polymer.
In the above known reaction, however, when the reaction time from the start of reaction exceeds 10 minutes, the reaction system causes gelation and precipitation and accordingly it is impossible to obtain the reaction product as a solution. That is, in the above processes, it is impossible to obtain a high-molecular polycarbodiimide solution having excellent stability.
Meanwhile, it is anticipated that imparting hydrophilicity to a polycarbodiimide will widen the application of the polycarbodiimide; to impart hydrophilicity to a polycarbodiimide, it is considered to adopt a method for introducing a quaternary ammonium salt into the main chain of the polycarbodiimide, which method is already known and disclosed in Japanese Patent Publication No. 5118/1967 or Japanese Patent Publication No. 24194/1967. Production of a quaternary ammonium salt-containing polycarbodiimide by the above-mentioned known processes for polycarbodiimide production causes gelation and precipitation, and it is impossible to obtain an intended product, polycarbodiimide solution.
A polycarbodiimide solution can be obtained by suppressing a carbodiimidization reaction; however, the resulting polymer is not endowed with heat resistance which is a feature of polycarbodiimide, and has only about the same heat resistance that urethane has, which is a detrimental drawback.
Thus, there has hitherto been produced no hydrophilic polycarbodiimide.